GB2145190A - Pneumatic spring acting as electrical switch - Google Patents

Abstract

A pneumatic spring such as is used to assist the opening and closing of vehicle bonnets includes a conducting tongue 6 attached to the piston 3 and ring 7 at the bottom of the cylinder. In the extended position, the tongue 6 contacts the cylinder 1 and a circuit is established between terminals 8 and 9, while in the contracted position, the ring (if insulating) interrupts the connection between tongue and cylinder. In an alternative embodiment, the tongue does not extend as far as the cylinder wall but does make contact with the ring, being of smaller internal diameter. In this case, the ring is conductive and completes the connection when the spring is contracted. The device can switch on, for example, the internal light of a car bonnet. <IMAGE>

Description

SPECIFICATION Pneumatic spring electrical connecting device As stated in the title of this Specification, this invention refers to a new electric connector which has been specially designed for pneumatic springs.

(The term "spring" used herein also meaning "strut" or the like).

Different types of pneumatic springs exist which are used to assist the opening and closing of vehicle bonnets, for folding and unfolding seats in the automobile field, for kitchen furniture and in numer ous other applications.

In certain cases, such as for example in the bonnet of a vehicle, or in the entrance door to a generally dark enclosure, it is sought to light the enclosure at the same time as the said element is opened and, consequently, that this illumination be interrupted, also automatically, on returning to the closed position.

The use is also known of pneumatic springs themselves, as the electrical connection element, as switches as such, to feed the respective circuit.

Electrical conduction is achieved thanks to the metal nature of their integrating elements and, for the switch, the relative displacement is used between the cylinder and the shank.

In this sense, we should quote British Patent 2,009,880, of STABILUS GMbh, in which the electrical circuit is established between the end areas of the pneumatic spring, through its actual cylinder and shank. Specifically, in the said British patent, one of the terminals is connected to the cylinder, this establishes permanent electrical continuity with the shank and the other terminal is connected to an insulating bushing, integrally joined to the free end of the shank, said second terminal forming a connecting finger which touches the metal part of the shank, interrupting the circuit when an electroisolant bushing, connected to the cylinder, is inserted between the shank and the finger in the maximum retraction position of the spring.

However, and as is known, in this type of springs, in the production process the shank is subjected to superficial treatment to ensure its hardening, treatment which usually consists of chrome-plating, nickel-plating or titration. These materials, deposited on the shank surface, are bad conductors of electricity, so that in the connecting point of the shank with the finger, an effect of "resistance" is produced which apart from causing a drop in tension with the consequent repercussion in the respective circuit, produces heating in the said area, due to this resistive effect, which can reach temperatures capable of deteriorating the plastic parts nearby.

The device which the invention proposes is centered specifically on a special layout to ensure the perfectly reliable connection and interruption of the electrical circuit in the movements of the spring.

More specifically, the device preconized is specially designed for pneumatic springs in which perfect electric insulation is maintained between the cylinder and the shank, in any of their relative positions, focusing its features on the means with which the connection is made between these elements, to be precise, after an initial outstretched stage of the spring.

For this, the plunger packing, shank head, made of an electroisolant material, preferably plastic, is pro vided with a metal strip, guided towards the free end of the cylinder, opposite the end through which the shank emerges, connected to the said packing preferably through the rivet itself with which the latter is fixed to the shank, so that said strip implies a radial projection which contacts the inner side of the cylinder and which, consequently, establishes elec trical continuity with it, as both the shank and the cylinder are made of metal.

In the end of the cylinder opposite the shank outlet, a bushing is arranged, with an electroisolant nature, preferably plastic, so that in the position of maximum retraction of the spring, said plastic bushing is inserted between the cylinder and the strip linked to the shank, interrupting the electrical continuity between these elements.

Obviously, in the free ends of the cylinder and shank, the relevant connection terminals are placed, to fix the spring in the feed circuit of the respective light point it is wished to supply, when the spring stretches.

As a complement to the structure disclosed, it has been foreseen that the cylinder be assisted by a plastic case which isolates it electrically from its surroundings.

Maintaining the organization quoted above and in order to vary the line of action of the assembly, it is feasible for the said plastic bushing associated to the cylinder end opposite the end where the shank emerges to be made of metal, in which case the strip linked to the plunger packing will be so arranged that it does not contact the side surface of the cylinder, unlike what happened in the previous case, while electrical connection is made in the spring's position of maximum retraction, a situation in which said strip will contact the metal bushing connected to the bottom of the cylinder. Obviously in this case the electrical connection will be maintained while the spring is in the position of maximum retraction, being interrupted in any partially extended position and, naturally, in the maximum extension situation.

To complete the description to be given below and in order to assist a better understanding of the features of the invention, a single sheet of drawings is attached to this Specification, as an integral part thereof, in which with an illustrative and unlimiting nature, and in its single figure, a side elevation view and diametrical cross-section has been shown of a pneumatic spring provided with the new electric connector which constitutes the object of this invention, said spring having been shown in two end positions, with maximum extension in a continuous line and with a discontinuous or dotted line in the minimum extension position.

In the light of this Figure it can be seen how the electric connector device which the invention proposes is applicable to a pneumatic spring made up through a cylinder 1 and a shank 2, with any configuration and conventional structure, but with the particularly that the packing 3 corresponding to the plunger of the shank 2 is of an electroisolant nature and that the said shank 2 emerges through the opening corresponding to the cylinder 1,through a likewise electroisolant guide bushing 4.

The invention is centered on the fact that to the packing 3, opposite the actual shank 2 and through the screw itself or rivet 5 with which said packing is fixed to the shank, a strip 6 is connected which emerges radially and which approaches or is adapted to the inner surface of the cylinder 1.

On the other hand, in the end area of the cylinder 1, opposite the outlet of the shank 2, a bushing 7 is placed, duly fixed to the said cylinder.

The basic elements, i.e., the cylinder 1 and the shank 2 are provided in their free ends with connection terminals 8 and 9, with which the spring is inserted in the supply circuit of the pilot light or electric drive element concerned.

From the layout disclosed, the connector offers two working possibilites: If it is wished that the said spring produces a situation of electrical disconnection when it is retracted, the bushing 7 will be of an electroisolant nature, preferably plastic, and the strip or tongue 7 which emerges radially from the packing 3 will contact the surface of the cylinder 1. In these conditions, throughout the run of the shank 2, this strip 6 wil establish electrical communication between the said shank and the cylinder 1, except in the position of maximum retraction, in which the electroisolant bushing 7 is inserted between the strip 6 and the cylinder 1.

On the other hand, if it is wished that the electrical connection only be made when the cylinder is in the maximum retraction position, the strip 6, with the same structure, will be suitably formed so that it does not contact the inner surface of the cylinder, still maintaining considerable proximity to it, whereas the bushing 7 will be of an electroconductor nature, i.e., made of metal. In these conditions, throughout the run of the shank 2, the strip 6 is isolated from the cylinder and when the cylinder reaches the limit retraction position, the said strip 5 touches the bushing 7, closing the circuit in which the spring is intercalated through the terminals 8 and 9.

From the foregoing it can be deduced that in any event the electrical connection device preconized has an extremely simple layout, with the consequent beneficial economic repercussion which this implies, apart from offering absolute working reliability, due to its very simplicity.

It will of course be understood that the present invention has been described above purely by way of example and modifications of detail can be made within the scope of the invention.

Claims (5)

1. A new electric connector for pneumatic springs, being speciaily designed for springs in which the metal cylinder and shank are electrically insulated, thanks to the insulating nature of the packing corresponding to the shank plunger and of a guide bushing through which said cylinder shank emerges, springs through which it is sought to supply a light point or any other electric device, essentially characterized in that it consists of a strip rigidly joined to the shank packing and opposing the latter, said strip adopting a radial position, which has it free end arched and which approaches or contacts the inner face of the cylinder, whereas the latter, in connection with the opposite end of the shank outlet includes a bushing closely joined to the said cylinder, which substantially reduces its diameter and which the radial strip connected to the shank packing touches in any case, said shank and cylinder being provided in their free ends with respective terminals for inserting in the corresponding electric circuit to be controlled.

2. A new electric connector for pneumatic springs, according to claim 1, characterized in that the bushing associated with the bottom of the cylinder can be of an insulating or conductor nature, i.e. of plastic or metal, so that in the first case the strip linked to the shank packing makes permanent contact with the inner surface of the cylinder, until it reaches said bushing, which acts as an electric connector, while in the second case, when this bushing is metal, the said strip does not make contact with the inner surface of the cylinder, throughout the run of the shank, electric connection being made when sadi strip reaches the said metal bushing.

3. A pneumatic spring comprising a cylinder, a piston shank and a piston head, the cylinder and shank being electrically conductive and the head being non-conductive, and further comprising a guide bush fpr guiding the shank within the cylinder, an insulating ring located inside the cylinder at the end thereof remote from the guide bush and a conductive tongue extending from the piston head and in electrical connection with the shank, the tongue when away from the ring making contact with the cylinder to connect electrically the cylinder and shank and electrical connection between the cylinder and shank, being interrupted when the tongue contacts the insulating ring.

4. A pneumatic spring comprising a cylinder, a piston shank and a piston head, the cylinder and shank being electrically conductive and the head being non-conductive, and further comprising a guide bush for guiding the shank within the cylinder, a conductive ring of internal diameter smaller than the internal diameter of the cylinder located at the end of the cylinder remote from the guide bush inside the cylinder and a conductive tongue extending from the piston head and in electrical connection with the shank, the tongue being capable of contacting the ring but not the internal wall of the cylinder such that there is no electrical connection between the shank and the cylinder when the tongue is away from the ring, and electrical contact between the shank and the cylinder is made when the tongue contacts the conductive ring.

5. A pneumatic spring substantially as hereinbefore described with reference to and as shown in the accompanying drawing.